This invention relates to an automatic preheating system for a diesel engine having an electric suction heater employed therein.
The preheating operation of diesel engines with a precombustion chamber by means of a glow-plug has been automated; however, the preheating system for direct fuel injection type diesel engines by means of an electric suction heater seems to be backward in automation.
It is considered that the advancement in the automation of the system for heating diesel engines by means of a glow-plug was mainly attributable to the facts that because the electric current needed for preheating is low, the battery will not be completely discharged even if it is kept as it is until the engine starts after the completion of preheating, and that because the preheating systems employing a glow-plug are employed mostly in passenger cars, which are not subjected to severe vibrations and other restraints, electronic components can be employed easily, and also that drivers of passenger cars have demanded the automation of such a system.
Whilst, it is envisaged that the delay in the automation of the system for heating the direct fuel injection type diesel engines by means of the electric suction heater was attributable to the facts that because the electric suction heater consumes a high electric power it is required to start the engine immediately after the completion of preheating, and that since such a system is mainly employed in construction vehicles which are used frequently under severe vibrating conditions, it is difficult to employ electronic components which tend to fail under such vibratory conditions.
The electric suction heater is connected through the key switch of the engine with the power supply, and the arrangement is made such that when the key switch is turned to its preheating position an electric current will flow through the heater.
However, since if electric current continues to flow through the heater for an extended period of time a various kinds of troubles may occur, the key switch is arranged to be returned by a biasing spring from the preheating position to "off" position in order to prevent the negligence of operator in resetting the key switch once turned to the preheating position to "off" position.
Therefore, it is required for the operator to continuously hold the key switch at the preheating position and such an opeation is very troublesome for him.
In particular, it is a much burden for the operator to hold the key switch at the preheating position by his hand for an extended period of time under a low atmospheric temparature.